Voldemort: "The Elder Wand cannot serve me properly, Severus, because I am not its true master. The Elder Wand belongs to the wizard who killed its last owner. You killed Albus Dumbledore. While you live, Severus, the Elder Wand cannot truly be mine."

Snape: "My Lord!"

Voldemort: "It cannot be any other way. I must master the wand, Severus. Master the wand, and I master Potter at last."